I tried to send a message to a friend last night. They were on my mind, and I just wanted to reach out to say, "hi! I think you're awesome and really appreciate your friendship."
I sent this message as a text to the phone number I've used to reach them for ... the past decade. It's marked as a frequent contact on my phone, and I had years of chat history stored there as well.
Sometime in the past month or so, they changed their phone number.
Though I live in a different city and area code, I still have the same phone number I had in college.[ref]This threw my wife for a loop when we were still dating and she was hit with a hefty long-distance charge the first month of our relationship. I felt guilty and set up a local Skype number she could call instead.[/ref] People give frequently give me a hard time for keeping a long-distance number, particularly when I lived in Seattle for a time.
I keep the number for the same reason I keep my 14-year old AOL email address: it's the only way some people know to get in touch with me.
Information changes rapidly in the world around us - even more so in the world of the Internet. Alleged facts known today might be disproven tomorrow. Statistics and metrics from yesterday might prove irrelevant today. New knowledge is discovered, old retired.
Change is somewhat of a constant presence in information. Unfortunately, we treat addresses the same way.
Email addresses, IP addresses, web addresses (both domains and URLs), phone numbers. All of these resource identifiers are meant to be immutable - they'll always point to the resource they originally define. Unfortunately we treat them as we would any other piece of information.
How many times have you clicked a link in an article and had it break? Or visited a domain allegedly representing a local business and had it fail? Or sent an email to an old contact and had it bounce? Or tried to text/call a friend only to chat with a confused stranger instead?
We throw addresses around often as reliable means of accessing certain resources, only to have these addresses prove no less mutable than the information they point to. I know services like the Internet Archive aim to prevent this loss of data, but that's only one effort.
What other forms of information do you expect to be immutable but see change regularly? What can we do to help keep what should be reliable data truly static?